Twisted strut construction for marine bearing with forwardly mounted propeller



March 14, 1961 w, ERLBACHER 2,974,628

TWISTED STRUT CONSTRUCTION FOR MARINE BEARING- WITH FQRWARDLY MOUNTED PROPELLER Filed Oct. 20, 1958 United States Patent TWISTED STRUT CONSTRUCTION FOR MARINE rligllglgG WITH FORWARDLY MOUNTED PRO- Robert W. Erlbacher, 920 N. Fountain, Cape Girardeau, Mo.

Filed Oct. 20, 1958, Sal. No. 768,185

6 Claims. (Cl. 115-34) This invention relates to improvements in boat constructions and, in particular, in concerned with a specially designed strut or brace construction for a propeller hearing which is mounted to the rear of the propeller for the purpose of increasing the propeller efiiciency and eflective power of the vessel.

In marine construction efforts are continuously being made to increase the propeller and propulsive efiiciency of vessels in an effort to achieve the maximum power possible. In this direction it is a purpose of this inven- "tion to decrease the obstructions oiiered to the flow of water coming into and leaving the propeller toincrease 'the eificiency. Essentially, this is accomplished in the instant invention by mounting the propeller on the vessel at the front of the hearing which supports it so that 30 water being presented to the propeller is essentially free :and unobstructed.

The supporting bearing is rearwardly mounted to the propeller and is supported from the hull of the vessel by a special strut or brace construction. The struts of this invention are supported in the fashion of a V from -the hull of the vessel with the apex being formed on the propeller bearing, the term apex being used in the sense to present the broad configuration, although the struts actually do not merge but are slightly spaced from one another at their junction where they are connected to the bearing. These struts, at their junction with the bearing, are located at a slight angle to the axis of the propeller and the vessel in order to prevent a minimum of flow obstruction to the propeller wheel race, which leaves the rear or trailing edge of the propeller in a twisting motion much as in the form of a helix. The struts are twisted along their longitudinal axis so that where they are connected to the bottom of the hull they are substantially in line with the axis or" the vessel, since at this juncture and in the region adjacent the juncture the effect of the wheel race is negligible and a minimum amount of resistance in line with the vessel axis is desired adjacent the hull connection. The struts are further stream-lined in cross section and the entire structure has been presented in a fashion whereby the resistance to water flow is kept to a minimum to increase the efliciency or the propulsive effect of the propeller wheel and the passage of the vessel through the water.

Thus, by means of this invention there has been provided a propeller mounted forwardly of support struts with the propeller bearing being positioned to the rear of the propeller and a strut construction for the bearing in which a minimum of resistance is presented to water flow passingby the strut. This combination of the forwardly mounted propeller with no obstructions presented to its front and the construction of the strut lends itself to a rugged structure for large vessels, either of ocean going nature or river vessels, including tug boats and the like, and other marine vessels. The structure is relatively simple in construction yet rugged in nature and relatively uncomplicated by virtue of which the structural and operational efliciency have been substantially increased.

It is accordingly a primary object of this invention Still another object of this invention is to provide a strut construction for marine hearings in which the strut has an elongated cross section and is twisted from its junction with the hull of the vessel and its junction at the bearing.

Still a further object of this invention is to provide a strut construction for marine propeller bearings in which there are a pair or" struts which diverge from their junction with the propeller bearing to their junction with the bottom of the hull, and in which the cross section is elongated and has a major axis parallel to the axis of the vessel at their junction with the vessel, and in which the major axis of the strut is located at a slight angle at the junction of the struts with the bearing.

Still a further object of this invention is to provide an improved propeller bearing for marine vessels in which the propeller is forwardly mounted, and in which the struts have an elongated hydrofoil cross section and are twisted from an inclined angle to the axis of the vessel at the junction of the bearing to a junction at the bottom of the hull where the axisof the struts is substantially parallel to the axis of the vessel.

Still another object of this invention is to provide an improved bearing and strut construction for marine propellers which is relatively simple yet rugged in design and improves the efficiency of the propeller operation.

Further objects of this invention will appear in the detailed description which follows and will be further apparent to those skilled in the art.

For the purpose of illustration there is shown in the accompanying drawings a preferred embodiment of this invention. It is to be understood that these drawings are for the purpose of example only and that the invention is not limited thereto.

In the drawings:

Figure 1 is a fragmentary sectional view taken just to the rear of the propeller bearing mounting in rear elevation of a vessel hull equipped with the propeller bearing and strut construction of this invention;

Figure 2 is a view in section taken approximately on the line 22 of Figure 1 showing the strut construction at the region of the propeller; and

Figure 3 is a view in section taken on the line 3-3, of Figure 1 showing the strut construction adjacent the junction with the bottom of the hull.

In Figure 1 a vessel hull 10 is shown equipped with a propeller II, a bearing 12, and bearing struts or braces 13 and 14. As best shown in Figure 2, the propeller 11 has a propeller hub 16 and three propeller blades 17, I8 and 19. The rear of the propeller hub is mounted within the bearing 12.

The bearing struts 13 and 14 are similar in structure and, as shown in Figure 1, are mounted in substantially converging relationship at their juncture with the propeller hub. Generally, they diverge upwardly to the point of their connection with the support plates 21 and 22, which are mounted upon the bottom of the hull as shown in Figure 1. The cross section of the struts is streamlined, as shown in Figures 2 and 3, with the trailing sur- Patented Mar. 14, 1961 face being flat and designated by the numeral 24 and with the leading surface 25 being of a streamlined or hydrofoil configuration. At the junction of the connection with the support plate, both the struts l3 and 14 are positioned in such a manner that they are generally parallel to the axis of the vessel and the propeller, it being understood, of course, that the axes of the propeller and the vessel are themselves parallel. This is best shown at Figure 3.

The junction of the struts 13 and 14 at their connection with the propeller bearing is best shown in Figure 2. Here it will be seen that there is a jointure such that the general axis of the struts is located at a slight angle with respect to the axis of the propeller bearing, and is substantially normal to the propeller blade as shown in Figure 2. For the purpose of example this angle may be in the neighborhood of 25, but it will be understood, as will further appear hereinbelow, this angle may vary for different types of service of the vessel and also for different types of vessels. Thus, it will be seen that there is a twist in the cross section of the strut from the inclined juncture with the axis of the hearing, as shown in Figure 2, to the juncture with the hull of the vessel, shown in Figure 3, at which latter point the axis of the strut is substantially parallel to the axis of the vessel.

Operation For the best understanding of the nature of operation of this invention, a brief description should be given relative to the action of the propeller wheel and the wheel race that it creates through its rotation. If it can be assumed that the boat has no friction in its move ment through'the water and there is no resistance to the forward movement of the propeller, it can be visualized that the action of the propeller in the water would be similar to that of a screw going into wood. Thus, the water would open up in front of the leading edge of the propeller blades and the water would close up behind it'without any backward motion of the water. Under such a circumstance struts placed behind the propeller should have their elongated cross section located on an axis parallel to the axis of the vessel to offer the least resistance.

'On the other hand, taking the other extreme if it is assumed that the boat is run up against an immovable object, the propellers in turning act as a pump and, since there is no forward movement of the boat, the action behind the propeller is that of a stream of water being pumped backward by the propellers in a twisting backward motion in the general form of a helix. Under such circumstance the struts to oifer the least resistance should have a pitch matching the swirl of the water which would approximate the pitch of the propeller.

In the first illustration offered above, the boat has no slip and would desirably employ a strut having its longitudinal axis parallel to the axis of the vessel, whereas, in the latter case there is a one hundred percent slip and the pitch in the angle of the strut should approximate the pitch of the propeller. Under actual operating conditions the conditions are somewhat between the two illustrations and, in the practice of this invention, it has been found desirable on river tug boats to use an angular twist of the strut at the juncture with the propeller bearing in the neighborhood of around 25. It will, of course, be understood that where the load on the vessel is increased the resistance to motion through the water is likewise increased and that the angle should be increased for such circumstances. Conversely, where the load is decreased the struts can bemade of a lower angle and more closely approximating a parallel position to the axis of the vessel. It will also be understood that varying angular degrees may be used for other types of vessels depending upon the'prop'eller 'design and the'type of service.

In the drawings shown particularly for Figures 1 and Cit 2 the propeller when looking at it from the rear has a counterclockwise motion and this will throw out water to the rear in the form of a twisting helix in which the rotation is likewise counterclockwise. As appears in Figure 2, the water immediately iloaving the trailing surface of the propeller and, as shown by the arrows identified by the reference numeral 36-, will move substantially parallel to the axis of the struts in a manner where the least resistance is presented by these struts. Thus, it will be seen that the wheel race, as shown in Figure 2, will not be substantially blocked by these struts and will pass by and around them within a minimum of resistance.

At the top of the struts adjacent the region of their connection to the hull of the vessel the struts have a substantially parallel relationship to the axis of the vessel as further appears in the sectional view of Figure 3. Here the wheel race has no effect and, since the vessel is moving through relatively undisturbed water, a parallel position of the axis of the strut with the axis of the vessel is desirable to present the minimum of resistance.

It will accordingly be seen that by the twisted rclationship of the struts a minimum of resistance is presented both to the wheel race and to the movement of the undisturbed water past the vessel in the neighborhood of the juncture of the struts with the hull. By providing a forwardly mounted propeller without any strut or hearing structure in front of it, the water presented to the leading edges of the propeller is undisturbed and the eiliciency of the propulsive efforts is greatly enhanced. A substantial increase in efficiency in power has accordingly been made possible by this invention.

As explained above, various changes and modifications may be made in this invention as will be readily apparent to those skilled in the art. For example, the twisted struts may be employed in advance of the propeller where construction design dictates this and increased efiiciency compared to conventional struts will be obtained, since the swirl of the water in the propeller action actually commences before coming into contact with the blades. However, it is more desirable for the struts to be located to the rear of the propeller for best results. Such changes and modifications are within the scope and teaching of this invention as defined by the claims appended hereto.

What is claimed is:

l. A propeller support for marine vessels comprising a bearing having means thereon for supporting a propeller and support means connecting the bearing to the bottom of 'a vessel in spaced relation thereto, said support means comprising a connecting member extending from the bearing to a connection with the vessel, said member having an elongated cross section with the longitudinal axis thereof being inclined to the axis of the propeller and substantially normal to the propeller blade in the region adjacent the connection of said member to the bearing.

2. A propeller support for marine vessels comprising a bearing having means thereon for supporting a proeller, support means connecting the bearing to the bottom of a vessel at the rear of the propeller in spaced relation thereto, said support means comprising a connecting member extending from the bearing to a connection with the vessel, said'member being twisted to present a minimum resistance to water flow due to the action of the propeller wheel race and the movement of the vessel and having an elongated cross section with the longitudinal axis thereof being inclined to the axis of the propeller in the region adjacent the connection of said member to the bearing, and the longitudinal axis of said member being substantially parallel to the axis of the vessel away from the wheelrace and adjacent the connection to the vessel.

3. A propeller support for marine vessels comprising a bearing having means ithereon for supporting a1propeller turd support means connecting the bearing to the bottom of a vessel in spaced relation thereto, said support means comprising a connecting member extending from the bearing to a connection with the vessel, said member having an elongated cross section with the longitudinal axis thereof being inclined to the axis of the propeller and substantially normal to the propeller blade in the region adjacent the connection of said member to the bearing, said connecting member having a leading surface provided with a hydrofoil configuration.

4. A propeller support for marine vessels comprising a bearing having means for supporting a propeller at its forward end, and support means connecting the bearing to the bottom of a vessel in spaced relation thereto, said support means comprising a plurality of connecting members extending substantially radially from said bearing in diverging relation to separate connections with the bottom of the vessel, said connecting members having an elongated cross section with the longitudinal axis thereof being inclined to the axis of the propeller and substantially normal to the propeller blade in the region adjacent the connection of said member to the bearing.

5. A propeller support for marine vessels comprising a bearing having means thereon for supporting a propeller and support means connecting the bearing to the bottom of a vessel at the rear of the propeller in spaced relation thereto, said support means comprising a plurality of connecting members extending substantially radially from said bearing in diverging relation to separate connections with the bottom of the vessel, said connecting members being twisted to present a minimum resistance to water flow due to the action of the propeller wheel race and the movement of the vessel, and having an elongated cross section with the longitudinal axis thereof being inclined to the axis of the propeller in the region adjacent the connection of said member to the bearing, and the longitudinal axis of said member being substantially parallel to the axis of the vessel away from the wheel race and adjacent the connection to the vessel.

6. A propeller support for marine vessels comprising a bearing having means for supporting a propeller at its forward end, and support means connecting the bearing to the bottom of a vessel in spaced relation thereto, said support means comprising a plurality of connecting members extending substantially radially from said bearing in diverging relation to separate connections with the bottom of the vessel, said connecting members being twisted to present a minimum resistance to water flow due to the action of the propeller wheel race and the movement of the vessel, and having an elongated cross section with the longitudinal axis thereof being inclined to the axis of the propeller in the region adjacent the connection of said member to the bearing, and the longitudinal axis of said member being substantially parallel to the axis of the vessel away from the wheel race and adjacent the connection to the vessel, said connecting members having a leading surface provided with a hydrofoil configuration.

References Cited in the tile of this patent UNITED STATES PATENTS 669,804 Parsons et al Mar. 12, 1901 1,549,564 Slocum Aug. 11, 1925 1,605,376 Schmitt Nov. 2, 1926 FOREIGN PATENTS 932,593 Germany Sept. 5, 1955 

